Re: [rtcweb] I-D Action: draft-ietf-rtcweb-data-channel-04.txt

Michael Tuexen <Michael.Tuexen@lurchi.franken.de> Mon, 04 March 2013 18:46 UTC

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From: Michael Tuexen <Michael.Tuexen@lurchi.franken.de>
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To: "MARCON, JEROME (JEROME)" <jerome.marcon@alcatel-lucent.com>
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Cc: Randell Jesup <randell-ietf@jesup.org>, "rtcweb@ietf.org" <rtcweb@ietf.org>
Subject: Re: [rtcweb] I-D Action: draft-ietf-rtcweb-data-channel-04.txt
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On Mar 4, 2013, at 3:36 PM, MARCON, JEROME (JEROME) wrote:

> 
> Randell,
> 
> Thanks for this update. There are some points not (yet) explained in the text:
> 
> 1. Following the SDP opening handshake, are the data channels implicitly opened, or does the offerer send one DATA_CHANNEL_OPEN message per new data channel ?
> 
> 2. "channel is available to send as soon as the DATA_CHANNEL_OPEN has been sent". And the SACK received I guess ?
The SACK is an SCTP level ack. So you only know that the SCTP stack of the peer has received it,
so you don't know if the application has received it or even processed it. So if you want some
sort of ack, you need an application level ack. This was done in the 3 way handshake stuff which
was in the older version.

In this version, the sender sends an DATA_CHANNEL_OPEN as the first message and the receiver has
to buffer user messages until the DATA_CHANNEL_OPEN message has been received in case of reordering
in the network and using unordered delivery for user messages.

Best regards
Michael
> 
> 3. Assuming an endpoint creating a new offer (e.g. to reflect a change in media streams) while an SCTP association is already established. In this case, what does the SCTP association m-line contain: the unchanged list of data channels contained in the initial offer (which created the SCTP association), or the list of data channels currently opened, or .. ?
> 
> 4. What happens if the SDP Opening Handshake agreed on some data channels using the 'chat' subprotocol, and later on an endpoint creates in-band a new channel with 'file transfer' subprotocol ?
> 
> Jerome
> 
>> -----Message d'origine-----
>> De : rtcweb-bounces@ietf.org [mailto:rtcweb-bounces@ietf.org] 
>> De la part de internet-drafts@ietf.org
>> Envoyé : lundi 25 février 2013 23:40
>> À : i-d-announce@ietf.org
>> Cc : rtcweb@ietf.org
>> Objet : [rtcweb] I-D Action: draft-ietf-rtcweb-data-channel-04.txt
>> 
>> 
>> A New Internet-Draft is available from the on-line 
>> Internet-Drafts directories.
>> This draft is a work item of the Real-Time Communication in 
>> WEB-browsers Working Group of the IETF.
>> 
>> 	Title           : RTCWeb Data Channels
>> 	Author(s)       : Randell Jesup
>>                          Salvatore Loreto
>>                          Michael Tuexen
>> 	Filename        : draft-ietf-rtcweb-data-channel-04.txt
>> 	Pages           : 13
>> 	Date            : 2013-02-25
>> 
>> Abstract:
>>   The Web Real-Time Communication (WebRTC) working group is 
>> charged to
>>   provide protocol support for direct interactive rich communication
>>   using audio, video, and data between two peers' web-browsers.  This
>>   document specifies the non-media data transport aspects of 
>> the WebRTC
>>   framework.  It provides an architectural overview of how the Stream
>>   Control Transmission Protocol (SCTP) is used in the WebRTC 
>> context as
>>   a generic transport service allowing Web Browser to 
>> exchange generic
>>   data from peer to peer.
>> 
>> 
>> The IETF datatracker status page for this draft is:
>> https://datatracker.ietf.org/doc/draft-ietf-rtcweb-data-channel
>> 
>> There's also a htmlized version available at:
>> http://tools.ietf.org/html/draft-ietf-rtcweb-data-channel-04
>> 
>> A diff from the previous version is available at:
>> http://www.ietf.org/rfcdiff?url2=draft-ietf-rtcweb-data-channel-04
>> 
>> 
>> Internet-Drafts are also available by anonymous FTP at:
>> ftp://ftp.ietf.org/internet-drafts/
>> 
>> _______________________________________________
>> rtcweb mailing list
>> rtcweb@ietf.org
>> https://www.ietf.org/mailman/listinfo/rtcweb
>> 
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